Dielectric resonator filters have been widely employed in space payloads and cellular base station equipment due to their compact size, good thermal stability and high Q performance.
Single-mode dielectric resonator filters, which have advantages in manufacturability and filter coupling configurations, have been widely used in wireless industry.
In recent years, multiple degenerate mode resonances in a dielectric resonator have also been explored, which utilize either the same type of modes with certain spatial symmetries or different types of modes resonating at the same frequency. U.S. Pat. No. 6,414,571 discloses a dual TM mode composite resonator for use in devices operating at microwave frequencies in the field of cellular telecommunications. U.S. Pat. No. 8,111,115 discloses dielectric resonator filters and multiplexers realized using full cylindrical or half-cut dielectric resonators.